Spark generated by ChemCam laser during tests

Radiation Assessment Detector

Clean room at JPL

Curiosity on tilt table

Building on the successes of the Spirit and Opportunity rovers, NASA later this year will launch its most extensive mission to Mars to date. It plans to send up a new rover packed with an array of 10 instruments for examining rocks, soil, and the atmosphere, including a powerful laser that will vaporize rocks from a distance and an instrument that analyzes samples for organic compounds.

At 2.8 meters long, the nuclear-powered, Mini Cooper-sized rover called Curiosity is twice as long and four times as heavy as its Spirit and Opportunity predecessors, NASA says.

Inside a 25-foot-diameter space simulation chamber at NASA's Jet Propulsion Laboratory in Pasadena, Calif., during one of the final phases of testing of the Mars Science Laboratory rover last month, Curiosity was put through operational sequences in simulated Martian conditions.

Sealing in a near-vacuum environment, the chamber is filled with liquid nitrogen and cooled to minus 202 degrees Fahrenheit, and giant light panels simulate Mars' sunshine.

Seen here on March 8, with all of its primary flight hardware and instruments, technicians use a wand to map the solar simulation intensities at different locations inside the chamber prior to the start of tests, NASA says.

Here, engineers test out Curiosity's driving ability over varied terrain, observing the rover's Rocker-Bogie suspension system as it drives over uneven ground during tests at JPL, according to NASA.

Each of Curiosity's six wheels has an independent drive motor. The two front and two rear wheels have individual steering motors that allow the rover to make 360-degree turns in place; it also has increased mobility with wheels that are double the wheel diameter on Spirit and Opportunity. That gives Curiosity the ability to more easily climb and roll over high terrain.

The nuclear power system on board will enable Curiosity to operate year-round and travel farther from the Martian equator than is possible with solar-powered rovers.

Two small arms, mounted on Curiosity's mast (seen in this image just above the technician's hands), will act as a miniature weather station, monitoring wind speed, wind direction, and air temperature, according to NASA.

In this image, a technician installs the Rover Environmental Monitoring Station (REMS) in September 2010 inside a clean room at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Other sensors in the REMS, which is provided by Spain's Ministry of Science and Innovation and its Center for Industrial Technology Development, will monitor humidity and ground temperature, NASA says.

REMS also includes an ultraviolet-light sensor on the rover deck and an air-pressure sensor mounted inside the rover's body along with the instrument's data recorder and electronic controls.

A high-gain antenna on-board Curiosity allows direct communications between the rover and Earth, using X-band radio transmissions.

The Alpha Particle X-ray Spectrometer instrument on Curiosity will measure the chemical components in Martian rocks and soil, NASA says.

The instrument bombards targeted samples of rock and soil with alpha particles, or helium nuclei, and X-rays; NASA says it then reads the resulting signature alpha particle and radiation that is given off and revealing which elements and how much of each are in the rock and soil samples.

Nicholas Boyd (left), a graduate student at University of Guelph in Ontario, and principal investigator Ralf Gellert prepare to install the Alpha Particle X-ray Spectrometer sensor head during testing at NASA's Jet Propulsion Laboratory, according to the agency.

"APXS was modified for Mars Science Laboratory to be faster so it could make quicker measurements. On the Mars Exploration Rovers [Spirit and Opportunity] it took us 5 to 10 hours to get information that we will now collect in 2 to 3 hours," said Gellert, the instrument's principal investigator. "We hope this will help us to investigate more samples."

The Sample Analysis at Mars (SAM) instrument, built at NASA's Goddard Space Flight Center in Greenbelt, Md., will examine samples of Martian rocks, soil, and atmosphere for information about chemicals that are important to life and other chemical indicators about past and present environments, NASA says.

The SAM instrument includes a mass spectrometer built by NASA Goddard, a gas chromatograph contributed by France's national space agency, and a laser spectrometer built by JPL.

Robotic arms will deliver drilled rock and soil samples to 74 on-board sample cups, heating samples to about 1,000 degrees Celsius in its two ovens.

With the rover flipped upside-down and its belly pan removed for access to the interior, technicians at JPL position SAM above the rover and install the instrument package.

"It has been a long haul getting to this point," said Paul Mahaffy, from NASA's Goddard Space Flight Center, describing the engineering challenges involved in creating such complex, compact instrument clusters. "We've taken a set of experiments that would occupy a good portion of a room on Earth and put them into that box the size of a microwave oven."

One of SAM's primary objectives is to check for carbon compounds called organic molecules, which are among the building blocks of life on Earth.

The clean room suits prevent contamination of biological material from Earth from showing up in results from the highly sensitive SAM system, which has the ability to detect less than one part-per-billion of an organic compound.

Although the laser beam itself is invisible, here we can see the ChemCam in operation during testing at JPL, showing a ball of bright white plasma emitted from the surface of a sample of iron pyrite crystal inside the sample chamber, according to NASA.

The Radiation Assessment Detector, or RAD, will monitor potentially dangerous levels of naturally occurring high-energy atomic and subatomic particles emitted from supernovas and the sun.

The instrument's telescope, seen here with a red "remove before flight" cover, faces upward with a 65-degree field of view. Two sensors monitor charged particles while a third detects the neutral particles produced by charged-particle radiation's interaction with the Martian atmosphere or ground.

On a tilt table in the Spacecraft Assembly Facility at NASA's JPL, we can see the Mast Camera (Mastcam) on the rover with two rectangular "eyes" near the top.

With one smaller opening for the telephoto eye (focal length of 100mm) and a larger one for the wider-angle lens that has a focal length of 34 millimeters, the two cameras can provide color images, high-definition video, and a combination for stereo views.

Original plans for Curiosity to carry a high-resolution 3D camera that "Avatar" director James Cameron was helping to build had to be scrapped when NASA apparently ran out of time to test the camera properly.